I'm just imagining Shimakaze making airplane sounds with her mouth.

Koucchan said:

I'm just imagining Shimakaze making airplane sounds with her mouth.

She is. Buu~n is Japanese onomatopoeia for something that's traveling at air at high speed.

not entirely unlike "zoom"

She really is like Renge from Non Non Biyori. I had thought they were similar but now the anime confirms it, down to the way she acts and make faces.